The recovery of petroleum from what was previously thought to be completely depleted oil wells, has become an important new source for petroleum in the United States. Since available reserves have become substantially depleted, new energy sources must be found in the form of recovering petroleum from fields which were thought to be depleted, and from which recovery was previously thought to be unprofitable by existing methods. Since only a relatively small fraction of the oil available in the so-called depleted fields was removed, there remains a substantial available petroleum source within those fields previously considered to be depleted.
Conventional pumping methods are, of course, unsatisfactory. There is lacking both sufficient pressure and sufficient quantity of oil to lend themselves to the conventional techniques of oil recovery. Increasingly, therefore, it has become necessary to turn to these abandoned oil fields and to develop techniques and methods for the secondary recovery of oil which exists in plentiful but less extractable forms. The art has not lacked for various proposals to accomplish secondary recovery: pressurizing oil wells by flooding with water, steam, and injection of air pressure, have all been tried, and with varying degrees of success. The principal problem is how to promote a material flow of oil, which is frequently of high viscosity, causing it to flow in such quantities and along established flow patterns within the oil bearing strata, to make recovery feasible.
Repressurizing oil wells: heating the substrate to reduce the viscosity of oil; flooding oil wells for regeneration purposes, have all met with only marginal success. Of course, as the cost of petroleum increases, even these marginal methods may become economically feasible, but there still remains outside the grasp of the art a completely satisfactory method for secondary oil recovery.
Examples of prior art which were sought to exploit secondary oil recovery on a commercial basis, are those teachings contained in Carpenter U.S. Pat. No. 4,037,655, "METHOD FOR SECONDARY RECOVERY OF OIL", issued July 26, 1977, and Hogg, U.S. Pat. No. 2,134,610, titled, "OIL SAND HEATER", issued Oct. 25, 1938.
Part of the reason why secondary recovery effort has remained unsuccessful, is the difficulty of regulating conditions of gasification, and of maintaining a favorable energy balance between energy requirements for gasification heating, and the yield in the form of energy, from the recovered oil. So long as the balance of energy input to output remains at its present level, the price of petroleum would have to substantially increase before the existing methods would prove practical.